Last Updated : February 2, 2022

The 2022 Hunga Tonga-Hunga Ha'apai Eruption, Kingdom of Tonga: Terrain change detected by ALOS-2 data

Terrain change Observed by Synthetic Aperture Radar (SAR)

Released: Jan. 26, 2022, update Feb. 2 2022 Japanese version of this page


Hunga Tonga-Hunga Ha'apai volcano, which is located 60 km north of Nukuʻalofa, erupted on Jan. 15, 2022 (UTC). In order to understand terrain changes due to the eruption and the status of Tongatapu island, we analyzed ALOS-2/PALSAR-2 data.
  • Clear terrain changes are observed in the central portion of Hunga Tonga-Hunga Ha'apai volcano (Figures 1, 2, 3, 4).
  • In Tongatapu island, there are regions where reflection intensities are reduced after eruption (cyan; surrounded by yellow lines), which may suggest that the regions are submerged due to tsunami or tidal changes (Figures 5, 6).

SAR Data

Date Time
Incidence Angle
1 2019-12-14 23:08 Des. Right W
2,4 2020-04-09
23:15 Des. Right F-F
3 2022-01-17 23:01 Des. Right W
5,6 2020-03-07
23:08 Des. Right F-F

*1 W: ScanSAR (Wide), F: Stripmap (Fine)
(cf. ALOS-2 Project / PALSAR-2 (JAXA))

SAR intensity image of Hunga Tonga-Hunga Ha'apai Volcanic Island

2019-12-14 SAR intensity image

Fig. 1 2019-12-14 SAR intensity image[PNG: 351KB]

2020-04-09 SAR intensity image

Fig. 2 2020-04-09 SAR intensity image[PNG: 342KB]


2022-01-17 SAR intensity image

Fig. 3 2022-01-17 SAR intensity image[PNG: 313KB]

2022-01-27 SAR intensity image

Fig. 4 2022-01-27 SAR intensity image[PNG: 336KB]


RGB composite image of Tongatapu Island

RGB composite image

Fig. 5 RGB composite image (2020-03-07/2022-01-22) [PNG: 919KB]

RGB composite image(closeup)

Fig. 6 RGB composite image(closeup) (2020-03-07/2022-01-22) [PNG: 1MB]

※RGB composite image
We assign the SAR intensity image of the first observation to Green (G) and Blue (B) channels, and that of the second observation to Red channel. If scattering intensity of a specific area decreases in the second observation (e.x. the area has been submerged by the sea), the area is depicted by cyan (GB).
(Additive color process using SAR amplitude images)

Analysis range

range image

Fig. 7 Analysis range

Analysis by GSI from ALOS-2 data of JAXA.
These results were obtained through the activity of the SAR analysis working group of the Coordinating Committee for Prediction of Volcanic Eruption.


ALOS-2 (Advanced Land Observing Satellite 2) launched by Japan Aerospace Exploration Agency on May 24, 2014

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Geography and Crustal Dynamics Research Center
Crustal Deformation Research
MUNEKANE Hiroshi: Head of Division
Space Geodesy Research
KOBAYASHI Tomokazu: Head of Division